Process of reducing ores.



PAT'ENTED NOV. 15, 1904.

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uw.; f. im cn. u van H. F. BROWN. PROCESS OFRBDUCI-NG DRES.

v APPLICATION FILED MAY 11, 1903.

UNITED STATES Patented November 15, 1904.

i. Annaud" HORACE F. BROWN, OF OAKLAND, CALIFORNIA.

PROCESSv OF REDUCING OFES.

SPECIFICATION forming part of Letters Patent No. 774,980, dated November15, 1904.

Application'iled May 11, 1903. Serial No. 156,551. (No specimens.)

To all la7/bmw it 771mm/ concern:

Be it known that I, HoRAoE'F. BROWN, a citizen of the United States',residing at Oakland, county of Alameda, State of California, haveinvented certain new anduseful Improvements inw Processes of ReducingOrcs; and I do hereby declare the following to be a full, clear,andexact description of the same.

The present invention relates to an improved process for the reductionof metallic ores or such ores wherein the constituents are freed throughthe agency of a reducing heat, to the action of which the ore issubjected, the term reduction as herein employed being used in itsgeneral sense as meaning the complete separation of the constituents ofthe ore or the treatment thereof ,prior to the delivery of the ore actedupon to a collecting means for the final act of separation.

Ordinarily in the treatment of ore inwhat is known as a stack or blastfurnace charges of ore, fluxes, and fuel, usually ,in the form ofcharcoal or coke, are alternately fed in, forming a column from eight tosixteen feet in copper and lead smelting practice and from forty toeighty feet in iron.- smelting. Twyers are introduced immediatelybelovs7 this column of charges anda blast of air forced in, the pressurerequired being governedsomewhat by the height of the column and thenature of the material, usually from eight to sixteen ounces and as highas forty-eight ounces. This excessive blastpressure develops anexceedingly high local temperature, establishing what is termed aLfusing Zone, extending upward from the twyers a probable average oftwofeet. Owing to the obstruction of the materials composing the charge,the blast and products of combustion do not pass uniformly upwardthrough the mass, but seek channels through which they rush with greatforce and velocity. To a degree the whole charge is aecte'd by thereducing properties of the heated gases that pass upward, and inproportion as all the elements of the charge are thus affected theprocess of reduction is facilitated. The burning of the coke has athreefold effect on the process-first, that of supplying heat forfusion; second, furnishing the required carbon for a reducing agent;third, displacement, which leaves the chargeA more or less porous as thecoke is consumed. In what is technically known as matte-smelting? thereis no reducing action, but silnply a concentration, the sulfur in thecharge combining with the iron and copper forming a copper-iron matte,which collects all the values of gold and silver. The excess of ironcombines with the silica, lime, and alumina. &c., forming a slag whichcarries with it all vthe non-metallic impurities. The grade of the matteis prede termined by the amount of available sulfur in the charge. YInlead-smelting and in the smelting of copper oxids the reducing action ofOO (carbon monoxid) gas serves to deoxidize' the previously-oxidizedmetals, reducing them to the metallic state, the silicates, &c., goingoff in the slags. Some of the sulfur is eliminated in the blast-furnace,especially where a hot blast is used, which raises the grade of thematte; butin the usual practice the excess of sulfuris burned olfprevious i to charging .the furnace.

In iron-smelting the oxidized ores are subjected tothe reducing actionof OO and gradually deoxidized in the slowly-descending column as theheat increases.l The height of the column is suiiicient to give time forcomplete reduction before the Zone of fusion is reached. The timerequired depends largely upon the condition of the ore, and as it isnecessary to charge the ore in coarse pieces a great height of stack isrequired.

rl`he theory and practice of ore reduction by smelting is based upon thecombining or fluxing action of ythe different ingredients of the charge.Materials that of themselves are almost infusible and at best under adestructive heat are readily fused at a comparatively low temperatureYwhen combined with the proper iuxing elements. 1n ore reduction bysmelting the chief element found in the gangue rock is silica,practically anjnfusible material, with more or less iron in the form ofan oxid or sulfid. Molten silica (biOf) Willcombine with iron in theform of ferrous oxid (FeO3) in practically equal amounts, and so greatis their aflnity that this combination l takes place practically to theexclusion of IOO all metals. in the charge, so there is an excess ofiron in the slag's, what is called a scouring slag is the result, and soviolent is the action of this excess of iron that it attacks thesilicious material of the bottom and the walls of the crucible orfurnace and causes destructive deterioration of the same. To neutralizethe free acid of the slag and to render it more fluid,a fixed proportionof lime (CaO) is added. Iron and sulfur combine, in round figures, inthe proportion of fifty-two per cent. sulfur (S) and forty-eight percent. iron, (Fe.) and so strong is this affinity that this combinationtakes place under all conditions, and

only by the oxidation of the sulfur can other i than an iron sulfid orwhat is known as "iron matte be produced. This matte has the property ofcombining with all of the metal contents of the charg'e, having' anunlimited capacity for taking' up gold, silver, and copper, theproportionate value being' governed entirely by the amount of sulfur.Consequently the first step in the concentration of the valuable metalsby smelting is to eliminate the excess of sulfur. Hitherto this has beenlargely done by a preliminary roasting under a heat much below fusion.

The disadvantages resulting from the foregoing' treatment and which thehereinafterdescribed process seeks to obviate, so as to reduce the costof reduction, are: (a) The losses in flue-dust, owing to the unavoidableamount of lines already in the ore and the decrepitation of the variousingredients of the charge under heat; (b) the loss of metallic gasesforced out too rapidly to be acted upon by the carbon monoxid and which,even if' acted upon, are carried out by the powerful ascending blast;(c) the tendency of the charge to become compact, owing' to the greatweight of the load that must be sustained, the uneven distribution ofthe heat and reducing-gases through the charge, and

the imperfect reduction resulting from such causes. To overcome thesedifficulties and to permit the use of hydrocarbon fuel, as oil or gas orof powdered charcoal, coke, or coaldust, as well as to utilize the heatgenerated in the rapid oxidation of sulfur and to conserve all possibleunits of heat, l have invented a simple and effective method or processfor the complete reduction of the ore.

atmosphere permits of the passage of the finely-divided particles in astate of suspension and segregation, so that every particle of the oreis acted upon individually by the said highly-heated non-whirlingatmosphere. The

The necessary fluxes, it will be un- Should there be an excess of iron lsecond step resides in subjecting the particles as they pass beyond thezone of the oxidizing atmosphere to the action of a whirling reducingatmosphere which conveys the ore downward through a reducing zone of thestack within which the ore is being treated. This atmosphere is soregulated that as it passes down the stack of the furnace a vortex isformed which brings the segregated particles together, which vortex alsoforms and maintains a zone of concentrated heat, so that instantcombination and fusion takes place. To successfully accomplish thisdesired end, it is necessary to prevent a diffusion of heat by expansionof the gases, which requires that the furnace-shaft be of practicallyuniform size from end to end or, preferably, slightly contracted tow-ardits bottom. The whirling action of the reducing zone gathers togetherthe particles of ore received therein in a segreg'ated condition 'andprolongs their travel through the furnace-stack, resulting in completefusion within the stack or during the travel of the particles throughthe zone of reduction.

In carrying' out the improved process for the reduction of ores the oresand fluxes are crushed to a finely-divided state, to the end 'that amore rapid chemical action may be gained during the travel of the oresthrough the zone of reduction.

Any suitable form of a stack-furnace may be employed in connection withthe working' of the process hereinafter described, one style of furnacecapable ofsuceessful use being' fully set forth and described in LettersPatent of the United States No. 689,062, issued to myself on the 17thday of December, 1901. However, a simpler form of furnace capable of usefor various ores is set forth in the annexed drawings, wherein- Figure lis a vertical cross-sectional view taken through the furnace-shaft, feedmeans for the ore, and through the hopper or storagechamber into whichthe crushed or pulverized ore is fed, said View being' on line x fc,Fig. 3 of the drawings, viewed in the direction of thearrow. Fig. 2 is alongitudinal sectional view disclosing the same features in section asare set forth in Fig. l of the drawings, also the collecting' basin orhearth for the reduced ores, the exhauststack, connections whereby theutilized heat may be directed into the hopper or storage-chamber for theore for the purpose of dehydrating' the ore previous to its being fedinto the reducing-blast, also disclosing in the manner of arranging thefurnace where the same is .to be utilized in connection with use for therecovery of quicksilver or for use in connection with the manufacture ofsulfuric acid; and Fig'. 3 is a crosssectional plan view taken on linea, Fig. 2 of the drawings, said View disclosing the arrangement of thehydrocarbon-burners.

In the drawings the numeral l is used to in- IOO dicate a verticalfurnace-shaft, the upper end portion of which is formeel into or hasattached thereto a combustiondchamber 2. A short distance above thecombustion-chamber is arranged a vibratory feed-plate 3, which isactuated by the eccentric 4 by means of the connecting-rod Any suitablemeans may be employed for operating the eccentric 4- as, for instance, adrive-belt 6, Working over belt-wheel 7, attached to the shaft 8,carrying the eccentric 4. The vibratory feed-plate 3 controls theoutlet-opening or spout 8 of the ore-receiving hopper or storage-chamber9, which is arranged immediately above the said feed-plate 3. Preferablywithin this hopper 9 is located a series of staggered angles or ilaterally-projecting partition-plates 10, so that l the ore is heldspaced within the said hopper. The ore or material to be treated isintroduced into this hopper by any suitable means in a finely crushed orpulverized condition.

Below and connected with the shaft 1 is located the collecting-chamberor hearth 11, which receives the treated material delivered from theshaft 1. From this hearth or collecting-chamber extends vertically theoutletstack 12 for the waste products of combustion from the shaft 1.Connection is made between the stack 12 and the hopper 9 by means of thefines 13 14, the former being controlled by a damper 15. Where thematerial to be treated requires to be dehydrated prior to beingdelivered into the shaft 1, the waste products of combustion arepermitted to enter the orehopper 9 by opening the damper 15. The hotproducts of combustion will then circulate throughout the openingsformed in the body of ore within the hopper by the staggered angles orplates, the heated gases absorbing all moisture of the tinely-pulverizedore very rapidly and finally escaping back into the exhaust-stackthrough the connecting-Hue 14. The ore or material is thus completelydehydrated, so that it is charged to the furnace at a heat to cause theimmediate ignition of all sulfur and to permit of reduction to begin atonce. y

rl`he reducing-fuel utilized within the combustion chamber for theproduction of a strong reducing atmosphere is oil or other carbonaceo usfuel ejected into the combustionchamber 2 in excess of the free oxygen,thus developing an excess of superheated carbon Inonoxid and activehydrocarbon gases which gives to the shaft a strong reducing atmosphere,which acts tofuse the material as carried through the zone of reduction.The reducing Zone extends approximately the entire length of the shaft1, although if necessary to produce a more strongly reducing atmosphereor Zone than that obtained from the carbonaceous gases of oil fuelfinely-powdered coke or charcoal can be fed in with the ore or be blownin at any desired point. The amount of this solid carbon thus admittedwill be govl erned by the need of such form of carbon for reduction. Thedraft of the furnace is such that a downd raft is given to the shaft 1,so that the travel of the reducing-blast is in a downward direction orfrom the combustion-chamber toward the hearth or collectingl means forthe reduced material, to this extent being the reverse of the ordinaryblast-furnace.

To insure a more complete combustion and a more perfect and somewhatlonger Contact of the ore and heat, the burners 16 for the oil fuel areso arranged within the combustionchamber that the flame is given aspiral or rotating motion, which will follow down the shaft, making alonger travel or path of travel for the falling ore. The gentle frictionof the walls of the stack will cause the gases to hang slightly, whichwill tend to form a vortex down the center of the stack through whichthe falling material will pass, keeping free of the outer walls. Thiswill prevent accretion and also, being a non-conducting medium, thegases will prevent the falling ore from being cooled.

The ore is fed by the vibratory feeder into the combustion-chamberthrough a highlyheated downwardly-moving non-whirling atmosphere inafinely pulver-ized or crushed condition and in suspension is deliveredto the reducing-dame, and thus carried downward with the movement of theblast through the reducing zone, which, as before stated, isapproximately the ent-ire length of the said shaft.

Where ore is being treated for the recovery of Quicksilver, thefurnace-shaft is formed with an inclined bottom 17, which defiects thewaste material into any suitable collecting device. The fumes arecarried off from the shaft through an outlet-pipe 18, which exhaust-pipeleads to or connects with any suitable means for collecting or forrecovering the Quicksilver from the fumes.

lln case the process is employedv for treating' ore for the manufactureof sulfuric acid a damper 18 in the exhaust-stack is closed and thefumes exhausted through the outlet-pipe 19 and treated thereafter in theusual manner.

lVhatever style of furnace construction be utilized the process ofreduction by passing the finely crushed or pulverized ore through ashaft in contact with and in the same line of travel as the travel ofthe hydrocarbon or reducing blast is the same. The described process isa continuous one in contradistinction to the independent-charge systemheretofore employed.

The Zone of reduction within the furnaceshaft may properly be defined asexisting between the points (t Figs. 1 and 2 of the drawings. Vhile thezone of reduction is dcfined as existing between the points a b it mustbe understood that the atmosphere maintained between the vibratoryfeed-plate 3 and the combustion-chamber 2 is the highly-heateddownwardly moving non whirling atmos- IOO phere to the action of whichthe ore is first subjected during its travel through the stack. In thepresent case no distinction is made between an oxidizing and a red ucingatmosphere, inasmuch as the terni "reduction is einployed to cover suchaction as takes place between the points a b, or what has beendesignated as the reduction zone.

I am well aware ot' the fact that heretofore the roasting and slneltingof ore has been accomplished by passing nulverized ore throug'h a stackin contact with a downwardly-nioving body of heat-such as described inLetters Patent No. 516,662, granted to J. J. Storer March 20, 1894i; butin such furnace the ore is not iirst subjected to the action ot' anapproximately non whirling highly heated downwardly-inoving atmosphereand thence conveyed through a whirling body of downwardly-travelingreducing atmosphere, which collects the segregated particles o'tl ore bycreating' a vortex. The devices set forth in earlier Letters Patent, No.41,250, granted I/Vhel# pley @t al. January 12, 1864, and No. 103,006,granted Arey May 17, 1870, are also known to me; but neither of thesedevices discloses my method ot' treating thev ore.

Having thus described my invention, what is claimed as new, and desiredto be protected by Letters Patent, isw g The` process of reducing oresas a continuous operation which consists in iirst passing the ore in atinely crushed or pulverized con'- dition through a non-whirlingatmosphere, and then subjecting the highly-heated ore to the action ot'a whirling heated atmosphere rnoving in the saine direction as thetravel of the falling body of ore.

In witness whereof I have hereunto-set rny hand.

HORACE F. BROVN. Witnesses:

N. A. ACKER, D. B. RICHARDS..

